Dielectric ceramic composition, ceramic substrate, and method for producing the same

Abstract

A dielectric ceramic composition includes about 10% to about 40% by weight of BaO, about 20% to about 65% by weight of SiO 2 , about 6% to about 40% by weight of Al 2 O 3 , about 1% to about 15% by weight of B 2 O 3 , about 0.3% to about 3% by weight of Cr 2 O 3 , and about 1% to about 40% by weight of ZrO 2 . A multilayer ceramic substrate has a laminated structure including an inner layer portion and outer layer portions that have a smaller thermal expansion coefficient than that of the inner layer portion. The use of the dielectric ceramic composition for the outer layer portions enables the ceramic to be resistant to erosion caused by a plating liquid used for plating external conductive films, thus maintaining good adhesiveness between the external conductive films and the outer layer portions.

1. A ceramic substrate having a laminated structure comprising:
 outer layer portions and an inner layer portion, the outer layer portions and the inner layer portion including a SiO 2 -based crystal phase, a content of the SiO 2 -based crystal phase being less in the outer layer portions than in the inner layer portion so that the outer layer portions have a smaller thermal expansion coefficient than the inner layer portion; wherein 
 the outer layer portion includes a dielectric ceramic composition comprising about 10% to about 40% by weight of BaO, about 20% to about 65% by weight of SiO 2 , about 6% to about 40% by weight of Al 2 O 3 , about 1% to about 15% by weight of B 2 O 3 , about 0.3% to about 3% by weight of Cr 2 O 3 , and about 1% to about 40% by weight of ZrO 2 , the dielectric ceramic composition being sintered; and 
 the inner layer portion is made of materials having substantially the same composition as materials of the outer layer portions except for the content of the SiO 2 -based crystal phase, and the inner layer portion includes substantially no zirconium. 
 
     
     
       2. The ceramic substrate according to  claim 1 , wherein the dielectric ceramic composition further comprising about 0.1% to about 3% by weight of at least one of Y 2 O 3 , CaO, MgO, and SrO. 
     
     
       3. The ceramic substrate according to  claim 1 , wherein the dielectric ceramic composition includes tetragonal zirconia as a ZrO 2 -based crystal phase including zirconium. 
     
     
       4. The ceramic substrate according to  claim 1 , wherein the SiO 2 -based crystal phase is at least one of quartz and cristobalite. 
     
     
       5. The ceramic substrate according to  claim 1 , wherein a conductor pattern primarily including one of silver and copper is disposed on at least one of a surface of the ceramic substrate and inside the ceramic substrate.